Let's be frankly controversial here: why Odoo should be responsible to give for free 10 years of subscriptions because legislation in Germany (Thailand or Ouagadougou) says so?

The user (of a company) is responsible to chose a system and the corresponding backup / conservation that suits his business or industry. Trying to make Odoo morally and financially responsible for every company's fate in the world is absurd and unprecedented... It is like trying to sue Smith & Wesson in a murder case.

Rough translation of chapter 9.4 "Moving
dataside out of the productive system, change of system"

In case of a system change (switch of
system, migration), or when moving data with retention requirements
outside of the productive system, the hardware and software of the
original productive system cannot be switched off unless the following
requirements are met for the remaining retention time:

1) Data with legal obligation for
retention (including meta data, master data, movement data and
associated links) must be moved in full and with the same quality into a
new system, database or archive system that complies in full with
regulations. If data conversion is required, it must be limited to the
data format (e.g. date or currency format), no content change is
allowed. All conversion changes must be documented ...2) The new system or archiving system
must allow an equivalent level and quality of analysis and evaluation of
the data under retention as the original system

Otherwise, the original hard- and
software of the productive system has to be kept together with all data
until the retention period expires.

In other words, keeping a 1-user DB in Odoo online would cover the
requirements. A download of the Postgres DB or a conversion into Excel
would not, as it would not provide equivalent analysis, and change of
data cannot be restricted as required.

Other countries may be different, but the overall requirements are
usually similar.

A possible solution would be to allow for read-only access for at least
one user, once an Enterprise license expires.

But companies
are legally required to keep their records for periods that can vary
from 5 to 10 years, sometimes more.

The above makes
it ERP SaaS not a viable option for most businesses.

That's what you say but it's not our feedback
from the market. (in terms of customers feedback & sales figures)

Whether you use Odoo Enterprise or Odoo Online,
you always have access to your data through PostgreSQL. It's not an
issue. I don't think we have lost a single customer based on that
assumption (we have 4000+ customers). It's a common practice in the
industry: if you don't pay for your software, you can not use it
anymore. (but you still own your own data through an open format:
PostgreSQL)

With Odoo Online, you can download your DB at any
time and access with PSQL, on Odoo Enterprise or keep a 1-user DB and
desactivate all others user to access through the enterprise UI if you
prefer.

The whole eco-system / business model of Odoo
relies on extra features in Odoo Enterprise that are not in Odoo
Community. And this model allows us to finance both the evolution of
Enterprise and Community editions. So, it's a good thing.

Having a path to keep using the Enterprise
features without having to pay for it (e.g. putting these features in
Odoo Community, directly or through third party apps) is a non sense and
would kill the sustainability of Odoo (as a company and product) in the
long term. It's a good thing to have features in Odoo Enterprise that
are not in Odoo Community.